In this section we state some notions of \(G\) -equivariant homotopy that will frequently appear in the rest of the paper.
The exposition will be sketchy and very focused to our goals; the reader interested in a thorough treatment of the subject is referred to [1]} for the theory of \(G\) -\(CW\) -complexes and actions on them, to [2]} for the theory of classifying spaces and to the first part of [3]} for Bredon homology.
